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I was training a woman for precision rifle shooting when she showed me her defensive handgun: a S&W M&P Bodyguard 380. This is a very small pistol: 5.25″ long, 4″ high, and just 0.75″ thick! Its dimensions make it easy to carry concealed, but can make it tricky to shoot.

This woman’s hands are almost as large as mine (which are 8″ long and 3.5″ wide mid palm), so I asked to see how she was able to handle such a small gun. Through practice on her own, she had concluded that even though she is both left-handed and left-eye dominant she shot it better with her right hand. Since it’s a double-action-only gun with a long, heavy trigger, she had resorted to pulling the trigger using the second knuckle. She noted that doing this she would often hit the magazine release with the tip of her trigger finger, but she didn’t know how else to run the gun. She also couldn’t figure out how to get her support hand on the gun, and so she presented it with the largely ineffective “teacup” hold.

The same guidance for holding guns that fit can be applied to holding undersized guns. Of course, the first order of business was to nix the idea of pulling the trigger with anything other than the center of the first joint of the strong hand’s index finger. (With large hands it can often be necessary to arch the trigger finger outward, but you never compromise on this point.) Then I showed her how to follow the usual steps of establishing a proper handgun grip:

Push the firing hand web between the thumb and trigger finger as high on the grip as possible.

Find a “home” position for the trigger finger outside the trigger guard, and then close the remaining fingers and palm snugly around the grip.

Now snug the support hand up and around the gun and trigger hand in order to maximize contact with its palm and fingers.

Ensure that the support thumb and index finger don’t interfere with the gun’s controls or the trigger pull. (Typically the support thumb will rest parallel and ahead of the trigger hand’s thumb. The support index finger needs to find a home too, and while that is often atop the knuckle of the trigger hand’s middle finger, on some guns it can instead find a consistent grip on the front of the trigger guard.)

Today I’m going to show a project that exploited the Chronos 1.4 at high image resolutions and at the lower end of its temporal resolution (i.e., frame-rate): What does handgun recoil look like, and how can a shooter control it?

I took a rusty shooter to the range with his Sig P239 chambered in .357SIG. This is an excellent concealed carry gun shooting arguably the ideal cartridge for defensive handguns. However, since the fully-loaded gun weighs only two pounds it has somewhat snappy recoil which requires training and practice to handle well.

Stepping through the video frames we can see that this pistol’s “lock time” (the delay from when the trigger is pulled until the hammer hits the primer) is 5ms. Also, from the moment the trigger is pulled, it takes 18ms for the slide to cycle to the rear, and 63ms to return to battery.

We filmed the shooter’s first few shots. He had forgotten some pistol fundamentals, including: proper grip, not anticipating the recoil, and following through each shot. (Granted, most of these problems can be detected or assumed even without high-speed video.) After retraining we filmed a few more shots. The improvement was remarkable. Beginning the refresher the shooter experienced muzzle flip of 40 degrees and consistently took over 60ms to halt the recoil of the gun. This composite overlaying the moment of discharge with peak recoil shows the slide already returned to battery by the time the shooter has stopped the recoil:

After retraining, the shooter was able to keep muzzle flip under 20 degrees and stop the recoil in under 40ms. (This was accompanied, of course, by faster and more accurate shooting.)

The sort of bullet-freezing high-speed video that has become familiar to YouTube audiences still requires a Phantom or Photron camera that runs well into five figures. However, there is finally a “pro-sumer” level high-speed video camera that fills the niche between 3-figure “action cameras” and those 5-figure professional cameras: The self-contained Chronos 1.4 is launching at $3,000 and offers 1.4Gpx/s throughput on a rolling 4-second buffer, which ranges from 1280×1024 @ 1,057fps to 640×96 @ 21,649fps! Aimed Research recently gave me an opportunity to test the beta version of this camera. I’ll show some of the cool things this camera can do over the next few posts.

Note that this was a beta device, and I didn’t have enough time to learn to optimize the camera at its limits. For example, here’s a 60gr .22 bullet leaving a barrel recorded at 9,000fps. With some more tweaking I expect I could have gotten the shutter speed low enough to show the bullet as a solid in each frame instead of a blur:

With time resolution in the thousands of frames per second we can see a lot of hidden phenomena. The following video of the same 10/22 rifle shooting the same 60gr .22LR bullet was recorded at 2,356fps. One surprising thing we can clearly see here is that the bolt bounces off of the breech when returning to battery.

Another thing we can see is something we heard during recent sound level testing: The unusual 60gr .22LR load is 50% heavier than the bullets for which this action was designed, and the case is 0.2″ shorter. As a result, the case clears the chamber less than 1ms after the bullet leaves the barrel, which causes a significant amount of pressure (and sound) to vent out the breech of the barrel. (A standard 40gr round doesn’t open the breech until 3ms after the bullet leaves the barrel.) If we wanted to tune this gun for this unusual cartridge, video like this would really help us confirm how changing bolt mass and spring rates affects the action.

As a precision shooter I’ve never found a trigger that I thought was too light. Two of my AR-15s have CMC 3.5-pound drop-in triggers, and two of them have Timney 667S 3-pound triggers.

The drawback to light triggers on the AR platform is that there is a limit to how strong the hammer spring can be. Ammunition with notoriously “hard” primers (e.g., military or Russian loads) will often fail to fire with these match triggers. I even experience occasional failures to detonate match primers (e.g., FGM205M). Timney addresses this problem by offering a heavier hammer spring, but that increases the trigger pull of their 667S to 4 pounds.

Hiperfire came out with a brilliant trigger system they call the HIPERTOUCH 24 in which the hammer pivot point is offset and supplemented with two adjustable springs so that the hammer force is lighter when it’s on the sear but heavier when it’s striking (similar to the way compound bows use cams to make the drawn weight lighter than the release weight). Now that it can be found under $200, it is my top pick for AR-15 triggers.

The result is a 3 pound trigger that hits almost as hard as a standard military trigger.

This post follows the introduction to shots, pops, and sound pressure levels. Virtually all firearms create pressure levels above 140dB, which is the limit established in MIL-STD-1474D to avoid unacceptable hearing damage. Hence, we put suppressors on our guns to bring their peak noise down to “hearing-safe” levels.

Small subsonic loads, like a 40gr .22″ bullet leaving a suppressed rifle muzzle at just 1000fps, make peak sound levels that are roughly the same as manually cycling the bolt of the gun shooting them: about 120dB. (Without a suppressor the same loads meter about 148dB.)

Is Barrel Length Still a Factor with Suppressors?

Yes. Even with low-pressure .22LR ammunition we can see something interesting: Barrel length has a significant effect on muzzle report. Shooting the same loads through a rifle and a pistol (barrel length with AAC Element II suppressor 9″ vs. 25″ for the rifle) the muzzle report is about 6dB higher from the pistol.*

I also ran a variety of subsonic 300BLK loads through two different AR-15s using the same suppressor (an AAC Cyclone): one gun with an 8″ barrel, the other with a 16″ barrel. The shorter barrel produced peak sound pressures 3-7dB higher than the longer barrel (depending on the powder load, as we will see below).

Are Suppressors Effective on Autoloading Actions?

Yes. A common question is whether a suppressed autoloading (i.e., semi-automatic) gun is louder than one with a locked action. Modern autoloaders use gas pressure and/or momentum from the discharged round to eject the empty case and load a new one. This usually occurs while the bore still contains a significant amount of propellant pressure. I.e., some of the same propellant that produces the muzzle report comes out of the breech.

Once we add a suppressor can the breech report exceed the muzzle report? It turns out that it can if a gun is poorly tuned, but that with typical guns and loads designed for them it does not. For example, I tested both a .22LR pistol (the Buckmark) and 10/22 rifle (Feddersen-barreled Ruger). Whether I let the actions cycle normally or held the bolts closed, the peak sound levels were the same, with one exception: 60gr Aguila ammo – which is very exceptional ammunition: Its bullet is 50% heavier than almost any other .22LR, and it is loaded in a .22 Short case. As a result, the case unplugs the breech before the bullet even leaves the muzzle! Since there is no suppressor on the breech, on the rifle this releases pressure of 128dB (vs 121dB from the muzzle with the breech locked) and on the pistol it produces 130dB (vs 127dB from the muzzle with the breech locked). However, it is possible to tune these guns to this unusual round by using heavier bolts and/or springs to prevent the action from unlocking before the bullet has left the barrel.

Similar mismatches can be produced with other actions. In fact, just attaching a suppressor to a centerfire autoloader that wasn’t designed for one can be such a nuisance that many designs and components now allow for the gas system to be adjusted. But as another test: I ran a wide range of subsonic loads through my 300BLK AR-15 with its standard gas system in place (i.e., autoloading), and then with its gas port completely blocked (i.e., locked breech). The peak sound pressure levels were identical in each scenario.

Does Powder Load Make a Difference?

Yes. The standard subsonic 300BLK load uses a 10.4gr charge of a relatively slow powder in order to provide enough gas volume to cycle a wide range of guns. I have experimented with other loads to see how light a powder charge I can use while still cycling my guns and producing the same muzzle velocity (about 1000fps) with the same 220gr bullet. (The only way to do this is to use faster burning powders.) I hypothesized that lighter charges would also reduce noise. Testing with the LxT1 sound pressure meter confirms this:

This is a Larson Davis Class 1 sound level meter. With a response time of under 30 microseconds and sensitivity up to 177dB, this is the sort of instrument needed to accurately measure the sound levels produced by transient events like gunshots.
Since I didn’t want to sink over $3,000 into a sound meter, I was able to rent one from Aimed Research, which has become my go-to company for ballistic research equipment and expertise.

I’ll be posting the results of my research shortly. This post explains the basic science needed to fully understand the methods and results.

We use a decibel amplitude scale to describe sound pressure using the formula dBSPL = 20 log10(peak pressure/ambient pressure). Since we will only be talking about sound pressure levels going forward we will assume that all dB values refer to dBSPL.

We will be looking at explosive noise events that we will call “pops:” sounds dominated by a single, rapid peak in air pressure. The human ear is not very good at assessing peak “loudness” of short pops.* But the magnitude of that peak can predict both the audible distance of the pop and its potential to damage hearing of nearby listeners.

The distance at which we measure a sound is as important as the dB value, because sound pressure decays linearly with distance. On the decibel scale, this means that the same sound measured from twice the distance will be 6dB lower. As is customary, unless otherwise stated, all dB measurements will be given for a distance of one meter from the source of the sound.

*For example, I’ve never been able to hear the “first-round pop” that tends to occur with cold suppressors. But in my test data I did find many cases where the first round peak was 3-4dB higher than subsequent shots.

I haven’t been able to find any decisive reviews of Gemtech’s 42gr .22LR subsonic ammunition. I finally picked some up under $4/box and decided to wring it through my Feddersen-barreled 10/22.

Since my last precision testing of 10/22 rifles, I have also refined a testing process capable of higher sample volumes, so I decided to compare the Gemtech to these other subsonic flavors presently abundant in my stockpile. (Of course, since Gemtech’s ammo is supposedly optimized for use with a suppressor, this test was conducted with an AAC Element II screwed to the muzzle of the 16″ Feddersen match barrel.)

Testing

One thing that has made precision testing much easier is this universal machine rest I developed: After every shot it returns the gun to the exact same position (which can be confirmed by the 32x scope on top), so it’s easy to shoot a string quickly and with zero shooter error.

I’ve also become a little more disciplined with respect to fouling the barrel: When shooting a clean barrel, or changing ammunition types on a fouled barrel, I ignore the first five shots. Different rimfire ammo uses different lubricants, and it takes some number of shots before the bore is consistently coated in the new lubricant. Five shots isn’t really adequate to fully stabilize the bore. (A good bolt action rifle will show that ten or twenty shots are required for it to settle in.) But at the level of precision one can get out of an autoloading rimfire, five shots seems “good enough.”

At 50 yards (the test distance shot here), muzzle velocity variance doesn’t really come into play. But it certainly does at 100 yards and beyond. It was easy to prop a chronograph in front of the machine rest and record the velocity of every round fired during the testing.

Analysis

Another thing that helped streamline analysis was OnTarget’s TDS software. It can’t (yet) auto-detect multiple shots on a single target, but it does auto-detect the points of aim, and it makes marking the shots and groups fast and easy.

Usable thermal imaging is widely available under $1000, and digital “night vision” is getting close to supplanting perpetually too-pricey image intensifiers. I found enough businesses working in this space that I’ve decided to wait to see what comes to market, rather than pushing for the particular integrated consumer product I have in mind.

In the consumer gun industry:

I haven’t written about them, but Flat Line bullets have brought revolutionary monolithic projectiles for long-range shooting to the masses.

Two years ago I asked for a three-mode trigger. I still haven’t seen what I specified, but the Echo trigger is a clever variant I hope to try soon.

Mantis has promised a second generation of their IMU that mounts to gun rails and interfaces with smartphones, allowing us for the first time to conveniently quantify and analyze recoil effects on firearms.

Bullpups continue to storm the mainstream. If you don’t like any of the increasing number of native bullpup autoloaders (AUG, Tavor, RDB, RFB, PS90 etc.) you can find conversion stocks for many popular platforms like the M1A, Ruger 10/22, Saiga, et. al. The KSG pump-action shotgun can actually be found at retail. From Europe we have clever single- and double-shot bullpups that should eventually be available at reasonable prices in America.

I’ve had a Kershaw Cryo G10 for two years, and during that time I’ve pretty much stopped carrying any other knife. It clips and rides more comfortably in the corner of my pocket than any other. I love the SpeedSafe assisted opening feature. I haven’t abused it, but I can at least tell that the steel will take and hold a decent edge. And since it can be replaced for under $30 I don’t feel the need to baby it.

I took advantage of a sale this week to add three more SpeedSafes to my collection. Top to bottom is a Filter, Brawler, Cryo 155Ti, and my two-year-old Cryo: